2022/02/19 by S. Geier, M. Dorsch, Ingrid Pelisoli +5 · 35 citations
Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Astrophysics and Star Formation Studies #Binary number #Demography #Horizontal branch #Metallicity #Physics #Population #Radial velocity #Sky #Stars #Stellar, planetary, and galactic studies #Subdwarf #White dwarf #astro-ph.SR
paper · pdf · open access · doi:10.1051/0004-6361/202143022
published in Astronomy and Astrophysics 661, A113 (EDP Sciences) · 28 pages, A&A accepted
arxiv created 2022/02/19 · openalex publication_date 2022/03/07 · arxiv updated 2022/05/18 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Hot subdwarf stars represent a late and peculiar stage in the evolution of low-mass stars, because they are likely formed by close binary interactions. Here we performed a radial velocity (RV) variability study of a sample of 646 hot subdwarfs with multi-epoch radial velocities from Sloan Digital Sky Survey (SDSS) and Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) spectra [...] As diagnostics we used the fraction of RV-variable stars and the distribution of the maximum RV variations ΔRV\rm max. Both indicators turned out to be quite inhomogeneous across the studied parameter ranges. A striking feature is the completely different behaviour of He-poor and He-rich hot subdwarfs. While the former have a high fraction of close binaries, almost no significant RV variations could be detected for the latter. This led us to the conclusion that there likely is no evolutionary connection between these subtypes. Intermediate He-rich- and extreme He-rich sdOB/Os on the other hand are likely related. We conclude further that the vast majority of this population is formed via one or several binary merger channels. Hot subdwarfs with temperatures cooler than ∼24 000 \rm K tend to show less and smaller RV-variations. These objects might constitute a new subpopulation of binaries with longer periods and late-type or compact companions. The RV-variability properties of the extreme horizontal branch (EHB) and corresponding post-EHB populations of the He-poor hot subdwarfs match and confirm the predicted evolutionary connection between them. Stars found below the canonical EHB at somewhat higher surface gravities show large RV-variations and a high RV-variability fraction, which is consistent with most of them being low-mass EHB stars or progenitors of low-mass helium white dwarfs in close binaries.